6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.68 



1856; Drepanodus Pander, 1856; Scolopodus Pander, 1856; Oistodus 

 Pander, 1856; Pdltodus Pander, 1856. 



Family PRIONIODIDAE, new family 



Prioniodus Pander, 1856 ; Suhprloniodus Smith, 1907 ; Gordylodus 

 Pander, 1856; Belodus Pander, 1856; Ligonodina^ new genus. 



Family PRIONIODINIDAE, new family 



Gornuramia Smith, 1907; Ilindeodella^ new genus; Pachysomia 

 Smith, 1907; Lonchod'ma^ new genus; Prioniodina, new genus; Pri- 

 oniodella^ new genus; Bryantodus^ new genus; EupHoniodina^ new 

 genus; Hibhardella^ new genus; Lonchodus Pander, 1856; Valentia 

 Smith, 1907; Prionognathus Pander, 1856; Pcdmatodella, new genus; 

 Diplododella^ new genus; Synprioniodina^ new genus. 



FISH PLATES (dermal plates) 



Family POLYGNATHIDAE, new family 



Polygnathus (Hinde) Bryant, 1921; Ancyrodella^ new genus; 

 Palmatolepis^ new genus; Pander odelJa^ new genus; Polygnathellus^ 

 new genus, Gnathodus Pander, 1856; fCtenognathus Pander, 1856. 



SYSTEMATIC DESCRIPTIONS 



DISTACODIDAE, new family 



Conodonts consisting of a single, more or less oval tooth or main 

 cusp with a small undenticulated basal expansion. 



Distacodus Hinde, 1879 {Machairodus Pander, 1856, preoccupied, 

 Machairodia Smith, 1907) Acodus Pander, 1856, Acontiodus Pander, 

 1856, Drepanodus Pander, 1856, Scolopodus Pander, 1856, Oistodus 

 Pander, 1856, and Paltodus Pander, 1856 are referred to this family 

 which comprises the simplest forms of conodonts. The differences 

 between these genera as defined by Pander, are based upon the gen- 

 eral shape and curvature of the tooth and particularly upon its 

 cross section. These differences are shown in our text figure but 

 without specimens of tliese various types of structure we will not 

 attempt to give generic diagnosis. 



Genus DISTACODUS Hinde, 1879 



DISTACODUS RECTUS, new species 



Plate 9, fig. 22 



A simple, rather straight, elongate tooth, slightly flaring at base, 

 with an obtusely rounded ridge on the inner and outer sides and 

 a more sharply keeled one on the concave posterior side or edge. 



